The present invention is generally directed to layered imaging members, imaging apparatus, and processes thereof More specifically, the present invention relates in general to electrophotographic imaging members and more specifically, to electrophotographic imaging members having a charge transport layer that has been reinforced with a ladder-like poly(phenylsilsesquioxane) (PPSQ) represented by: in which n represents the number of repeating segments, and to processes for forming images on the member.
A photoreceptor with a reinforced charge transport layer refers, for example, to a device wherein the charge transport layer includes a ladder-like polysilsesquioxane, which is a strong hybrid material with a high glass transition temperature and excellent stability. Poly(phenylsilsesquioxane) can be introduced into the charge transport layer without modifying the charge layer preparation and manufacturing procedures. In embodiments, a small percentage of poly(phenylsilsesquioxane) components are doped in the charge transport layer to sensitize the chlorogallium phthalocyanine pigment in the charge-generating layer.
Numerous imaging members for electrostatographic imaging systems are known including selenium, selenium alloys, such as, arsenic selenium alloys, layered inorganic imaging and layered organic members. Examples of layered organic imaging members include those containing a charge transporting layer and a charge generating layer. Thus, for example, an illustrative layered organic imaging member can be comprised of a conductive substrate, overcoated with a charge generator layer, which in turn is overcoated with a charge transport layer, and an optional overcoat layer overcoated on the charge transport layer. In a further “inverted” variation of this device, the charge transport layer can be overcoated with the photogenerator layer, or charge generator layer. Examples of generator layers that can be employed in these members include, for example, charge generator components, such as, selenium, cadmium sulfide, vanadyl phthalocyanine, x-metal free phthalocyanine, benzimidazole perylene (BZP), hydroxygallium phthalocyanine (HOGaPc), chlorogallium phthalocyanine, and trigonal selenium dispersed in binder resin, while examples of transport layers include dispersions of various diamines, reference for example, U.S. Pat. No. 4,265,990, the disclosure of which is incorporated herein by reference in its entirety.
One problem encountered with photoreceptors comprising a charge generating layer and the charge transport layer is that the thickness of the charge transport layer, which is normally the outermost layer, tends to become thinner during image cycling. This change in thickness causes changes in the electrical properties of the photoreceptor. Thus, in order to maintain image quality, complex and sophisticated electronic equipment is necessary in the imaging machine to compensate for the electrical changes. This increases the complexity of the machine, cost of the machine, size of the footprint occupied by the machine, and the like. Without proper compensation of the changing electrical properties of the photoreceptor during cycling, the quality of the images formed degrades due to spreading of the charge pattern on the surface of the imaging member and a decline in image resolution. High quality images are essential for digital copiers, duplicators, printers, and facsimile machines, particularly laser exposure machines that demand high resolution images.
There continues to be a need for improved imaging members, and improved imaging systems utilizing such members. Additionally, there continues to be a need for imaging members of varying sensitivity, which members are economical to prepare and retain their properties over extended periods of time.
A number of current electrophotographic imaging members comprise charge transport components and polymer binders, such as N,N′-diphenyl-N,N′-di(m-tolyl)-p-benzidine (m-TPD) and a binder polycarbonate. Devices with this composition are susceptible to physical damage such as phase deformation, cracking and low wear resistance.
One feature of this invention is to improve the strength of electrophotographic imaging members photoreceptors by incorporating stronger inert components into the transport layer to, for example, allow for more stable photoinduced discharge characteristics curves.